The invention relates to a sensor based on surface wave components, consisting of a housing with at least one surface component, a fluid channel, and conduits for conducting high frequency signals to, and from, the housing as it is known from DE 44 17 170.
In the field of sensors, piezoelectric high frequency components, such as bulk oscillators, surface wave resonators, surface work delay conduits, and filters on a quartz or ceramic basis, are electrically contacted by way of bond or weld joints. The bond wires are often disposed in areas of the sensor which carry fluids and generate additional noise as a result of vibrations, corrosion, and different materials at the point of contacts. They require space for the provision of bond loops and contacts and they cause signal delays by needed components and fixing cement.
R. Steindl et al.: SAW Delay Lines for Wirelessly Requestable Conventional Sensors, Proc. IEEE Ultrasonic Symposium, discloses SAW components which are controlled passively by transponders with antennas by way of electromagnetic waves.
J. Freudenberg et al.: A SAW immuno-sensor for operating in liquid using a SiO2 protection layer, Sensors and Actuators B 76 (2001) 147–151 discloses a SAW chip which is coupled by induction via a current loop. The high frequency coupling by way of antenna loops however requires a relatively large space on the surface of the sensor chip. The coupling must be placed mechanically accurately in order to compensate for insertion damping changes at different antenna distances. In addition, the sender and receiver antenna impedances must be adapted for which additional component changes and installation damping changes are necessary. The complete signal is highly delocalized by the inductive part of the antenna coupling. Because of the large amount of over-recording consequently different coupling structures cannot be arranged in a spatially tight manner.
It is the object of the present invention to provide a sensor of the type described above which however is simple in design and small in size.